But some firms are instead using a system based on telling us the percentage of Guideline Daily Allowances (GDA) each product contains for calories, sugar, fat, saturates and salt.

And there are fears that companies using the GDA method are bewildering us with tricks such as using green backgrounds to present awkward figures - hoodwinking consumers who think green means healthy.

Research by consumer body Which praised the traffic light system - but slammed the GDA measurement for confusing shoppers. Chief policy adviser Sue Davies said: "We are calling on all retailers and manufacturers to use the FSA multiple traffic light scheme on the front of their packaging so that customers are able to easily identify which products are the most healthy."

And nutrition expert Juliette Kellow doesn't rate the GDA labelling either. She said: "GDAs don't tell us whether the figures are for men, women or children. It can make a big difference.

"GDA figures also seem to be frequently left off. And it's unacceptable to list the facts for what are hardly the healthiest foods with a green background. All it does is confuse people."

So we asked Juliette to highlight the misleading labels on some supermarket foods...

Kellogg's Coco Pops, 600g

PROBLEM: GDAs are for adults - and don't include milk

JULIETTE SAYS: "Coco Pops are eaten almost exclusively by kids, so why use adult GDAs? Also, who eats their Coco Pops dry? Including milk would not make a huge difference to the readings, so why not be transparent about it?

"Using traffic lights there would be green for fat and saturated fats, amber for salt and red for sugar."

Two snack pork, cheese and onion Melton Mowbray pies, 75g

PROBLEM: All the labels on the front have a green background, despite high fat and sat content.

JULIETTE: "Consumers will just get confused. If most of us see a load of green round the nutrition figures we're going to assume the product is healthy. But these pork pies would both have red marks on sats and fats under the traffic light system. This is a clever marketing ploy."

Boots mature cheddar and apple sandwich

PROBLEM: No labelling on front, even though saturated at contents are high.

JULIETTE: "Look carefully and you will see this sandwich takes up 55 per cent of your saturated fat intake, which would give it a red light.

"Fats and salts come in at around a quarter of your GDA - both amber. You'd want to stick to ambers and greens for the rest of the day after eating this."

Tesco macaroni cheese, 450g

PROBLEM: Label reveals it has 99 per cent of daily saturated fat allowance - on a green background.

JULIETTE: "This is 99 per cent of your sats GDA and 45 per cent of your fats, yet these are on green backgrounds. The colours are meaningless.

"Admittedly, the size of the portion is responsible for this but it's still wrong to paint them green. And there are no GDAs for kids."

Sharwoods Tikka Masala mild/medium, 420g

PROBLEM: No labels on the front and those on the back are in tiny print.

JULIETTE: "This label opts to use calories, fats and salts but they do not tell you what the actual GDA is for men, women and children.

"The figures that do exist are tiny. You would want to know that a third of a jar contained 31 per cent of your salt allowance."

Pot Noodle curry flavour, 95g

PROBLEM: No labels for children. Hides danger of high salt content

JULIETTE: "For a start, there is nothing on the front of the pot. For some measures the GDA for a child is not significantly less than that for a woman - which is what normally appears on labels.

"But for salt the GDA is 4g instead of 6g. With 2.4g in each pack, that makes a big difference to whether you'd feed one to your kids."

Cadburys Dairy Milk, 49g

PROBLEM: Ignores sugar and saturate GDAs.

JULIETTE: "Because the calories and fats figures do not seem that terrible, it's easy not to worry about the lack of information on sugars and saturated fat, but they are very high.

"Nine grams of sats is almost half a woman's GDA and 27.7g is almost a third of her daily sugar allowance. On the traffic light system this would be red for sats, fats and sugars."

Mr Kipling six chocolate slices

PROBLEM: No information on the front of pack and uses hard-to-read pie-charts.

JULIETTE: "The information given is per slice but these slices are not very big and it would be easy to eat more than one.

"GDA figures of 6.6 per cent for calories, 9.6 per cent for fats and 2.3 per cent for salt may sound OK but under the traffic light system the front of the pack would contain red spots for sats, fats and sugars with a green for salts alone."

Dairylea, eight thick slices

PROBLEM: The serving size is for just one slice.

JULIETTE: "You need long division to work out that in a 200g pack, the 25g serving they refer to is just one slice.

"Only 5.3g of fat per slice may not sound much and with a 70g GDA you may think you can give your kids a few without worrying, But actually this is a high-fat product."